WebGL: Error when creating texture from KTX ASTC 6x6 file

[BStringhamVRSK]

In WebGL (in Chrome browser), I'm getting an error message when creating a texture from a KTX file, which was created with MIPGEN, using the following parameters:
mipgen -f ktx -c astc_thorough_ldr_6x6

Run time error message:
WebGL: INVALID_ENUM: compressedTexSubImage2D: invalid format

I've tracked down the format enum value:
COMPRESSED_SRGB8_ALPHA8_ASTC_6x6_KHR = 0x93D4

Here's the code I'm using (in TypeScript)
texture = this._engine.createTextureFromKtx(byteArray, { srgb: isSRGB });
I've verified as best I can that the byteArray I'm sending is correct. When I change from a 6x6 compression block to 4x4, I still get the error, but it reports a different invalid enum (which matches the 4x4 format).

Using Filament 1.10.3
Is this a known issue? I thought I'd ask before attempting to try a bunch of different compression formats to find one that might work.

==== UPDATE: ====
It appears to me that the ASTC extension is not getting initialized, for some reason. I was assuming that, since I was using Chrome, the ASTC extensions would be supported. But, perhaps the hardware I am testing on does not support it.
I called:
Filament.getSupportedFormatSuffix("astc s3tc etc");
and only s3tc came back, so, I changed to that encoding, and the error messages disappear.
I would prefer ASTC, since both the quality and size are potentially better, but it looks like I may need to support both possibilities.

[BStringhamVRSK]

The answer seems to be:
Don't assume like I did, that a certain format will be supported. I needed to use S3TC compression instead of (or in addition to) ASTC.